1. Field of the Invention
The present invention relates to an optical device and to a projector.
2. Description of Related Art
There has been known a projector comprising a plurality of optical modulators each for modulating a light beam irradiated from a light source according to image information to form an optical image, a color combining optical device for combining the light beams modulated by the optical modulators, and a projecting optical device for projecting the light beams combined by the color combining optical device to project the formed image in the enlarged state.
Of these components, as the optical modulator, for instance, an optical modulator based on the active matrix drive system with an electro-optic material such as a liquid crystal sealed between a pair of boards is generally employed. More specifically, the pair of boards constituting this optical modulator comprises a drive board provided in the light beam incident side and comprising a data line, a scan line, a switching element, a pixel electrode and the like formed thereon for loading a drive voltage to a liquid crystal, and a counter board provided in the light beam irradiation side and comprising a common electrode, a black mask and the like formed thereon.
Further a light beam incident side polarization plate and a light beam irradiation side polarization plate allowing transmission of light beams having prespecified polarization axes respectively are provided in the light beam incident side and light beam irradiation side of this optical modulator respectively.
When a light beam irradiated from a light source is irradiated to the optical modulator, the temperature of the optical modulator often rises due to absorption of light by the liquid crystal layer or by the data line and scan line formed on the drive board, and also by the black matrix or the like formed on the counter board. Further, of the light beams irradiated from a light source, and also of the light beams having passed through the optical modulator, those not having the prespecified polarization axes are absorbed by the light beam incident side polarization plate and the light beam irradiation side polarization plate, which often generate heat in the polarization plates.
To overcome the problems in the projector having optical modulators therein, there has been proposed a projector having a cooling system for alleviate the temperature rise in an optical modulator with a cooling fluid (Refer to, for instance, Japanese Patent Laid-Open Publication No. HEI 3-174134).
Namely, the cooling system described in the reference above comprises a casing with the two edge faces opposing to each other opened and having a substantially rectangular form, and also comprises a cooling chamber with a cooling fluid filled therein. An optical modulator is provided on one of the edge faces opposing to each other with an incident-side polarization plate provided on the other edge face, and the optical modulator and incident-side polarization plate closes the opened opposing edge faces to form a cooling chamber. With the configuration as described above, the heat generated in the optical modulator and the incident-side polarization plate is directly released to the cooling fluid.
With the cooling system described in the reference, however, as a capacity of the cooling fluid sealed in the cooling chamber is small, the heat exchange capability between the cooling fluid and the heated optical modulator or the optical element including the heated incident-side polarization plate is rather low.
Further as a circulation speed of the cooling fluid sealed in the cooling chamber is slow, the cooling fluid is easily warmed up by the heated optical element, so that a temperature difference between the optical modulator and the cooling fluid becomes smaller.
For the reasons as described above, with the cooling device described in the reference, there is the problem that it is difficult to efficiently cool an optical element with a cooling fluid.